This invention relates to methods of forming micromachines and components. More particularly, it relates to a fabrication process wherein micromachine subassemblies on separate substrates are diffusion bonded together to form a united structure.
Micromachines are potentially useful for a wide range of applications requiring robust and complex miniature mechanisms, and particularly for forming an interface between complex microelectronic circuitry and the external world. Many such applications, however, require many discrete levels of components, some of which components are thick compared to the average component thickness, to provide the required functionality. Multiple component levels and thick components, however, are difficult to fabricate based solely on the planar microfabrication techniques known in silicon microelectronics and in such metallic-based fabrication techniques as LIGA (LIGA is a German acronym which stands for lithography, electroplating, and molding). Even when high-aspect-ratio fabrication techniques are used, maintenance of precise intercomponent separations and tolerances is often difficult. In addition, even though suitable techniques exist to planarize the surface of a micromachine subassembly, so that further growth and component definition can take place, problems and costs associated with such serial microfabrication dramatically limit the use of these techniques.
There is therefore a need for a method to enable assembly of micromachine subassemblies which require multi-level precision structures. A further need is for a method which can be used to assemble such micromachines in batches, preferably on the scale of entire substrate wafers. Application of such techniques to packaging of micromachines will also be useful to the industry.